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Daphne Bramham: A good reminder of the Big One’s potential

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Daphne Bramham

Publishing date:

December 31, 2015 • 3 minute read

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OK, it was an earthquake and the biggest one we’ve had in a decade.

But no damage has been reported despite the best efforts of journalists and politicians looking hard to torque the story for a) the nightly news or b) to bolster their calls for more earthquake proofing of public buildings.

No damage should have been expected because seismologists define what we had Tuesday as a “light” earthquake, and that was before it was downgraded to a magnitude 4.3 from 4.9.

People did report feeling their highrise buildings sway, beds moving; hearing dogs barking and sounds louder than a big truck rumbling by and more similar to a car crashing into a wall, or a teenage boy thumping down the stairs.

But it was slight enough that once again people’s reactions — and the breathless media coverage — have provoked parody.

One image being shared on social media is a photo of a plastic patio set with one chair knocked over and the headline: “Earthquake, Vancouver 2015! We will rebuild!!”

As that image suggests, we lack perspective here. Worse, even though we live in an earthquake zone, we don’t know very much about quakes, measurements or even what to do if we do have a Big One.

Here’s one of the most striking facts.

Even at 4.9 magnitude, Wednesday’s earthquake was not even close to half the size of the predicted Big One of 9.0, as the numbers might appear to suggest.

The Richter scale is logarithmic. So, a 9.0-magnitude quake — a “great” earthquake like the one off the coast of Japan in 2011 — is 15,848 times larger.

Even an 8.2 quake, which is believed to be the upper limit of a quake along California’s famous San Andreas Fault line, would only be six per cent as strong as the Japanese quake.

Our little earthquake is also pretty common — 30,000 of these light ones are recorded every year. In fact, it was only one of three of that size recorded in last two days in our region.

Haida Gwaii has had three quakes in the 4.1- to 4.3-range in the last month. What made Wednesday’s quake newsworthy is that it occurred in the province’s most-populated regions.

In April, Kitimat had a 6.2 magnitude earthquake. It wasn’t even reported in the local newspaper.

I don’t mean to be flippant about what happened. But I’ve been in California during several much larger ones.

One was a 6.1 magnitude earthquake that sent ornaments marching across tables, lamps swinging on the ceiling and made me feel as if I was in a plane flying through turbulence rather than with feet supposedly on terra firma.

Yet, more frightening was that it was so close to the San Andreas Fault that there was uncertainty about whether it was a foreshock for the Big One. It was not. But it was followed by hundreds of smaller aftershocks that ranged from 3.1 to 4.6.

It convinced me at the time of the need to prepare for a bigger earthquake. But over the years, I’ve become lax about that.

So, all this fuss over a small quake is a good reminder that many of us aren’t the least bit prepared for the big quake that seismologists say has a one-in-10 chance of happening within the next 50 years.

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It won’t just be inconvenient, as last September’s windstorm was for the half million residents who lost power for a few days. It will be awful and far beyond the worst of what most of us have ever experienced.

A shallow, magnitude 7.3 quake directly below Vancouver would result in 10,000 people dead, 128,000 injured and 100,000 people without shelter, according to Emergency Management B.C.

Its modelling suggests that nearly one in five buildings in Metro Vancouver would receive extensive damage and another one in eight buildings would suffer catastrophic damage.

If or when it happens, we’ll all have to somehow manage on our own. A minimum of three days is what the experts say. For some, it will likely be much longer.

We all ought to be ready with water, food and first aid supplies.

In fact, doing that along with putting together plans for evacuating and reconnecting with family and friends are New Year’s resolutions that we ought to make and keep.

Of course, we’re only human. Next week, the little quake will likely have been forgotten along with the resolve to plan for something that may (or may not) happen between now and 2066.

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